Technical Abstract:
Zebra chip disease (ZC), caused by the bacterium ‘Candidatus Liberibacter solanacearum’ (Lso), is of increasing concern to potato growers throughout the western United States and elsewhere. New potato cultivars are being developed that are tolerant of Lso such that infected tubers do not express ZC symptoms. Previous studies indicated ZC symptoms were associated with increased tuber levels of amino acids, sugars, and phenolics. Therefore, this study examined whether or not increases of amino acids, sugars, and phenolics occurred in Lso-infected commercial or potentially ZC-tolerant potato cultivars. Lso-infected tubers from the commercial, susceptible potato variety 'Atlantic' exhibited strong ZC symptoms. Levels of many amino acids, sugars, and phenolics were greater in infected 'Atlantic' tubers compared to those that were non-infected. By contrast, Lso-infected tubers from three tolerant cultivars, designated 'ARS7008', 'ZC73', and 'ZC74', did not exhibit ZC symptoms. Levels of amino acids, reducing sugars, and phenolics were not significantly different between non-infected and Lso-infected tubers from the three tolerant cultivars. These results provide evidence that potato cultivars that do not have physiological changes in response to Lso infection are unlikely to develop ZC symptoms. Thus, tolerance, rather than immunity, may be sufficient to mitigate effects of ZC disease.